A device of this type is known from DE-A-29 46 557. With this known device a circuit is switched on with the aid of the radial cam connected with the adjustment lever, which controls a magnet valve embodied as a 3/2-way valve. It controls the pressure supply of the servo motor from an underpressure source in such a way that under full load the exhaust gas return valve, which is controlled by the servo motor, is closed and under partial load it is opened. This opening state is furthermore affected by a further pressure sensor as a function of the rpm in such a way that the exhaust gas return valve is opened only starting at defined low rpm.
This device is relatively expensive and also has the disadvantage that the further pressure sensor is disconnected from the position of the adjustment lever (the signal arrives independently of the position of the adjustment lever). In addition, two circuits are required: an electrical one for the magnet valve control and a pneumatic one for the adjustment unit ARF.